Wireless power transmission is attracting attention. Since a radio wave with a high power density is transmitted in wireless power transmission using radio waves, in particular, it is required not to cause radio disturbance on wireless devices other than a power receiving device, and a power density of radio waves irradiated to a human body is required to be reduced to a predetermined value or less specified by international non-ionizing radiation protection committee (ICNIRP) or the like.
There has been proposed a technique of detecting an obstacle existing in a power transmission section from a power transmission device to a power receiving device, and changing a direction in which a radio wave is transmitted by the power transmission device so as not to irradiate the obstacle (person or animal).
However, estimation of a direction and a position of the obstacle requires hardware and software to realize a function for the estimation. In addition, since hardware and software of this type are affected by antennas, feeder lines, and peripheral components, regular or irregular calibration is required. Further, in estimating a direction and a position of the obstacle, an error occurs due to environmental conditions and the like. Furthermore, even if a main beam that maximizes the radiation of the radio wave is controlled such that the radio wave is not radiated at a position or in a direction of the obstacle, a radio wave is irradiated on a human body by a sub-beam generated secondarily, and a part of the human body is exposed to the radio wave if a range not radiated with the radio wave is too narrow, since the human body has a width.